Method of preparing neutral shellac salts



'photoengravi-ng solution, and the like.

various processed lacs, such'as' Patented Oct. 9, 1945 METHOD on 2,386,421., I PREPARING NEUTRAL it SHELLAC' SALTS Henry Hall Bassford, J r.,

or to U. S. Shellac Brooklyn, N. 'Y.,'assig-r1- I H Importers Association, Inc,

New :York, N..Y., a corporation of lNcvvYorlg. 1 N I )rawing. Application May '15, 1942 1 .3 Claims. 01. zoo- 1102) j.

This invention relates to a method of preparing neutral shellac salts. p

Aqueous alkaline solutions of shellac are used as hot stiileners, leather'andshoe dressings, varnishes for paper, floor waxes, inks, adhesives, I These solutions are frequently prepared using volatile alkalies such as ammonia and organic amines. They are made using native shellac as :well as refined bleached shellac; and hard *lac.

V The following difficulties have been reported by members of each of the above classes of shellac users. :In the first place the bleached grades of shellac deteriorate and become "insoluble after" two or three-months"standing, unless stored at temperatures common to refrigeration. Furthermore, even after standing a short time, the shellac tends to *sinter' together and form a hard resinous mass which must be broken up, in order to permit of'lts removal from the container. "In the second place, due to the slowness with which shellac dissolves in aqueous alkali'fit is necessary to heat said aqueous alkali to an elevated tem perature of at least 80 C. in order to obtain a reasonably rapid reaction. When aqueous alkaline shellac solutions are prepared, therefore,

using an open vessel, volatile amines and ammonia evaporate rapidly from solution and considerable losses occur before the "base can react with the acid groups of the shellac. This evolution of ammonia or amines constitutes botha nuisance and-a hazard, and, since additional alkali must be added to replace that lost by vola- "tization, constitutes a waste as well. Furthermore, under these conditions, accurate con-trolof the final solution is virtually impossiblem Although the "loss of base can be prevented, and

the shellac solution made conveniently, in a closed pressure vessel equipped with suitable mechanical gitation, the high cost of equipment of this type prohibits its use by most users of shellac. In the third place, it is frequently desirable to prepare neutral aqueous solutions of amine or ammonium salts of shellac. When these are prepared using shellac and an aqueous solution of the volatile base, the solution is stirred and heated until the shellac is dissolved, additional alkali being added to replace that lost through evaporation. The solution is then boiled until the excess ammonia or amine has been driven off. Under these conditions some hydrolysis (and consequent impairment) of the shellac usually takes place. Even if a closed vessel is used it is diflicult to prepare a neutral solution bleached shellac;

since the exact amount of alkali required is airficul-t to ascertain. The acid number of the various grades of shellac varies from 50 mg.

K'OH/gm. to over "100 mg. KOH/gm. 'Furthermore the acid number-of a particular grade will vary "dependent on'its source and subsequent storage" conditions. Even if the acid number is determined analytically the proper *quantity 'of the hot alkali-nesolution; with-resultant conalkali cannot be deduced; since uncontrollable hydrolysis of the first portion of lac dissolved by sumption of base,- occurs during the dissolution proc s volatile Thisinvention has as an'object' thepreparw tion of neutral salts of shellac with ammonia or amines A second object is the -preparation of a stable; free-flowing, powdered deriva ,tive of refined and "bleached-shellac, which does not 'sinte or become insoluble on storage at room temperature, A third object is the preparation of neutral aqueous varnishes by merely dissolving the neutral shellac salt in hot or cold water. A fourth object is the preparation of alkaline shellacsolutio'ns, containing a volatile alkali,"in an open vessel, withoutappreciable' loss of base throughevaporation. A' fifth object is the preparation of alkaline shellac solutions in such a rrioist vaporof the y upon; the correspondingshellacjsalt is formed manner that the aqueoussolution shall at all 7 mes have a pH of less than 7.5 thus minimizing the hydrolysis of the shellac during' the'dissolutionprocess. g The first object is accomplished by subjecting the shellac in a finely'fdivided"condition to the ammonia or amine, whereand'then convertingthis product to an essentially neutral salt: by aerating to remove "excess ammania or amine vapor.

The second object can be achievedeither by preparing the neutral saltof the shellac as de i scribed above, or by subjecting the shellac to a controlled amount of amine or ammonia vapor, sufiicient to neutralize any mineral acid which may be present in free or combined form but insuflicientto convert more than a small percentage, (for example 5%) of the shellac to the amine or ammonium salt. Alternatively, the finely divided shellac may be stirred or tumbled in a closed Vessel with 10 volumes of water containing ammonia or volatile amine slightly in excess of that required to neutralize the acidity of the shellac. The stirring is continued until the shellac swells and absorbs water, indicating formation of the shellac salt. The excess solution is then poured oil and the solid product dried tyla-amine; idimethylaminerand the like. 7

. ;;I'he-:1f 1 QW- n tainer, placed within the closed vessel. v -natively, an air circulating systern may. behin- .through aqueous H The 7 material; i

well ventilated. room for 1 Y Q .7 H V tially neutral ammonium shellac-ate. r

agitation;

,rthat a purppse offthis-inve aration: 01a r stable variety at room temperature for twenty-four hours, whereupon both the water and the small amount of excess ammonia or volatile amine which is absorbed in the shellac is removed by evaporation.

The other objects are readily attained by agitating the neutral shellac salt; prepared above, with three or more times its weight of hot water whereupon the shellac dissolves to form a neutral aqueous varnish, without loss of volatile alkali through evaporation, and without the :pH of the solution going above 7.5 at any time dur ing the dissolution process.

In this application the term clude all forms of lac, the secretion o'f the insectg' Tachardia Lacca Kerr, whether in raw; refined or manufactured form. Modified lac ,is taken to,

include all forms of lac which have been'imaterially modified by chemical means. "Bleached shellac" includes all forms of lac which have'been .decolorizedbya :bleachingprocess and include .l suchproducts as white shellac, decolorized hard -lac,; et cetera. a K

. amine gvolatile below about 12 3C: and having a dissociation constant in watersolution greater than;l0- is suitable for preparingneutral shellac salts.- Examples of lac," refined bleached :amines whmh are suitable are morpholi ne ethylene diamine, methexamples,,- in which gparts are Example 1- gqq parts of finely ground (preferably smaller than 40 mostly-refined l leached shellac are placed in, a closed vessel and maintained at. room tom perature. for twenty-four hourswhile heingsuhjected to moist ammonia gas hich -,can. heal tained, it desired; allowing 22,pa:rts of128? aqua amm n t eva r e: r m a s P r e,. n-.

A ter stalled in which air, saturated T. by bubbling ammonia, is placed, through the Other methods such as mixing anhydrousjammonia gas and steam may al employei shellac powder.-

spread. out .in trays ,and allowed resha e, in a twenty-four. hoursg to allow complete removal'of excess .ammoniafand The resulting product is, essen- N-eutral aqueous solution ,of this. Pmduc v we es s e ht, rme e e 852,95 F ,1 results after about twenty minutes form solutio' '7 mentioned earlier in this-specification "tion was the prepoi refinedhleached be easily prepareduby .agitatin the ammonium shellacate withethree to water, 'areferably shellac. varieties of this material, which deteriorate on storage at room temperature in from three to six months, invariably become practically insoluble in alcohol after eight hours air-drying at 60 C. The sample of refined shellac used in Example I became almosty completely insoluble after only "two hours at 60 CZ -The neutral'ammonium -sh ellac-'shall-in H i'actory for ammonia and low molecular weight aliphatic amines; such as methyl amine, div,methylami e, and. the like. -;*:however, it is desired to shellacate prepared therefrom, however, re-

-'mained completely soluble even after twenty-four hours air-ld ing at 7 Example 2 The process described in Example 1 is satis- In certain cases, prepare a neutral shellac salt of a higher boiling amine such as ethylene diamine or morpholine. In such cases the preceding processgrequires a prolonged time of expo'sur'e and may advantageously be replaced by r the followingprocedure. v

,ufiorwparts'byweight oifinelyjgroundishellac are .25 I device containing 300 partsofwaterand 5.5; parts placed. in a ball mill jar or other closed tumbling of morpholinen The mixture is tumbled until the t" are illustrative-oi my invention:

r r spread ut" mixturel in. the vessel-swells and tends toadhere together; indicating ;thatgreaction has occurred between 'thershellac, and morpholine, The I olution is their d a tedganath solid co tents ,toldryin open trays -at=room temp ra ura. p l The dried Jp'rp duct, t e. t 0

pholon ijumf shellacate is readily soluble in hot Y l. IA t 40.

water .to, ram a neutral aqueous 'varmsh, 5 5 :Havins ,describem my invention, -what 1 s claim and dlsirg 9 rseeure DYT Q WE r Ra entis as follows; a,

0d for. preparing a dry, neutral she1-- lac saltwof. volatile ;alk ali which comprises exposing the shellac, in finelyidividedform,;.to the moist vapor. .of a volatile. alkali untila shellac I I salt of a the @allrali is termed and. then aerating about 120'deg. cs'having a dissociation vconstant in-water solution greatenthan l0 ,--which com- 7 prises exposing 'theashellac in .fme1y, divided shellacate oithe amineis formed lac saltoi-a volatile organic amine, volatile below the amine' until a and; then aeratiorm, to the moist vvapor ,of

ping the-salt-to remove moisture and unreacted amoniurn shel-lacate which,comprises exposing the shellac; finely divided form; gas untila-shellacate 1-. thenaerating; the salt to remove moistureand I :unreacted ammonia. a;

i e: a

3. A method; for. preparing 1 dry,- neutralam to moistqammonia oi ammonia. is formed; and

assess; I i-J,

' We have found that the commercial 

